1. Field of the Invention
The present invention relates to a photocoupler, a method for fabricating the same, and a photocoupler fabrication apparatus. More particularly, the present invention relates to a photocoupler capable of reducing the mount area required to mount the photocoupler on an object, a method for fabricating such a photocoupler, and a photocoupler fabrication apparatus.
2. Description of the Related Art
The photocoupler is a device for removing noise generated in outputting a signal from an information processing unit such as a personal computer (PC) to external, and is soldered to a small card such as a personal computer memory card international association (PCMCIA) card connectable to an information processing unit.
A conventional photocoupler is shown in FIGS. 30 and 31. FIG. 30 is a cross-sectional side view of the photocoupler, and FIG. 31 is a schematic side view of a photocoupler fabrication apparatus.
The photocoupler, denoted by 8a, includes a pair of lead frames 83 and 84. The lead frames 83 and 84 support a light-receiving device 81 and a light-emitting device 82, respectively.
In more detail, the light-receiving device 81 and the light-emitting device 82, which are placed to face each other on the same optical axis, are attached to the lead frames 83 and 84, respectively, with bonding wires 85 such as gold wires. The light-emitting device 82 is pre-coated with a transparent silicone resin 86 for relieving stress at a junction and the like.
Transfer molding is then performed for the light-receiving device 81 and the light-emitting device 82 placed on the same optical axis, using a transparent resin. By the transfer molding, the light-receiving device 81 and the light-emitting device 82 are embedded in the light transparent resin to form a primary mold body 87.
The primary mold body 87 is then shaped by burring and tie bar cut. The lead frames 83 and 84 protrude from the sides of the primary mold body 87. The protruding lead frames 83 and 84 are then subjected to forming so that the base ends of the lead frames 83 and 84 are bent roughly at right angles with respect to the sides of the primary mold body 87.
The thus-formed primary mold body 87 is placed in a mold space D of a photocoupler fabrication apparatus (hereinafter, simply called an apparatus) 9 as shown in FIG. 31. The apparatus 9 is constructed of injection molds 91 and 92. The injection mold 91 is laterally slidable.
A light-shading resin is injected into the mold space D of the apparatus 9 with the primary mold body 87 placed therein, to form a secondary mold body 88 by the transfer molding.
The secondary mold body 88 is shaped by burring and tie bar cut. The ends of the lead frames 83 and 84 protrude from the bottom of the secondary mold body 88. Thus, the photocoupler 8a as shown in FIG. 29 is fabricated.
The thus-fabricated photocoupler 8a is mounted on a small card by soldering using the ends of the lead frames 83 and 84 protruding from the bottom of the secondary mold body 88.
With recent improvement in substrate wiring technology, objects on which devices are mounted, such as a small card, have not only enhanced in performance but also become smaller in size. In addition, the mount rate of devices to be mounted on an object, such as photocouplers, resistances, capacitors and transistors, on the object has increased. In view of these, it has become necessary to reduce the mount area required to mount each of such devices on the object.
However, to fabricate a photocoupler, consideration must be given to the following points: the double transfer molding for forming the primary mold body and the secondary mold body, the positional relationship between the lead frames supporting the light-receiving device and the light-emitting device inside the photocoupler, securing of a space for placing ends of the lead frames to be soldered to an object on which the photocoupler is mounted, and the like. The photocoupler therefore needs a body case large enough to satisfy these fabrication requirements, and thus reduction in the mount area required to mount the conventional photocoupler on an object is limited.
An object of the present invention is to provide a photocoupler capable of reducing the mount area required to mount the photocoupler on an object by eliminating a structurally unnecessary portion, and an apparatus and method for fabricating such a photocoupler.
The present invention provides a photocoupler comprising:
a pair of lead frames;
a light-emitting device placed on one of the pair of lead frames;
a light-receiving device placed on the other lead frame for receiving light emitted from the light-emitting device;
a primary mold body made of a light transparent resin for covering the light-emitting device and the light-receiving device; and
a secondary mold body made of a light-shading resin for covering the primary mold body,
wherein the pair of lead frames are bent in the secondary mold body, and outer side faces of terminal portions ranging from the bent positions to top ends of the lead frames are exposed at surfaces of the secondary mold body.
According to the invention, the pair of lead frames are bent in the secondary mold body. The outer side face of the terminal portion of each of the lead frames, ranging from the bent position to the top end thereof, is exposed at the surface of the secondary mold body. That is, the outer side faces of the terminal portions are not covered with the secondary mold body, and thus the mold amount of the secondary mold body can be minimized. As a result, the mount area required to mount the photocoupler on an object can be reduced.
In the invention it is preferable that the secondary mold body has a concave portion, and a top end of the terminal portion protrudes from the concave portion.
For example, the concave portion is formed at a position corresponding to the top end of the terminal portion, so that the top end of the terminal portion protrudes from the concave portion. Therefore, soldering of the secondary mold body to an object for mounting can be made in the concave portion. This eliminates the necessity of securing a space for soldering near the secondary mold body, and thus the mount area required to mount the photocoupler on the object can be reduced.
In the invention it is preferable that a thermoplastic resin is used as the light-shading resin.
The present invention provides a photocoupler fabrication apparatus for fabricating the photocoupler described above, comprising:
a pair of fixing molds for fixedly sandwiching the primary mold body therebetween vertically;
a pair of lead frame pinch molds placed on both sides of the fixing molds for pinching base ends of the pair of lead frames; and
a bending mold placed on outer sides of the lead frame pinch molds for bending the pair of lead frames fixedly pinched by the lead frame pinch molds,
wherein the pair of fixing molds, the pair of lead frame pinch molds and the bending mold define a mold space for the secondary mold body.
According to the invention described above, with the construction of the pair of fixing molds, the pair of lead frame pinch molds and the bending mold, the secondary mold body can be molded into a desired shape, while the mold amount can be minimized. As a result, it is possible to fabricate a photocoupler in which the mount area of the body case constructed of the primary mold body and the secondary mold body can be reduced according to the shape of an object on which the photocoupler is to be mounted.
In the invention, it is preferable that correction means for correcting a position of the primary mold body with the bent lead frames in the mold space is provided.
According to the invention, with the correction means, when the primary mold body with the bent lead frames is not in a desired position, the primary mold body can be moved to the desired position. Therefore, it is possible to form the secondary mold body in which the primary mold body is in a desired position without fail.
The lead frame pinch mold may be allowed to protrude in the mold space during the molding of the second mold body.
According to the invention, since the lead frame pinch mold is allowed to protrude in the mold space during the molding of the second mold body, a concave portion can be formed on the second molded body. This makes it possible to secure a space for soldering of the top end of the lead frame to an object on which the photocoupler is mounted, mold the secondary mold body into a shape according to the shape of the object, and/or prevent misidentification of the position of a component embedded in the body case.
In the invention, it is preferable that concave grooves for allowing the pair of bent lead frames to fit therein are formed on the lead frame pinch molds, and the lead frame pinch molds is permitted to protrude in the mold space in molding the secondary mold body so that top ends of the pair of lead frames fit in the concave grooves.
According to the invention, the lead frame pinch molds protrude in the mold space during the molding of the secondary mold body so that the top ends of the pair of bent lead frames extending from the primary mold body fit in the concave grooves formed on the lead frame pinch molds. Therefore, concave portions can be formed on the resultant secondary mold body, and the top ends of the pair of lead frames are allowed to protrude from the concave portions.
In the invention, it is preferable that cutting means for cutting away unnecessary portions of the pair of lead frames is placed on the outer sides of the bending mold.
According to the invention, since the cutting means for cutting away unnecessary portions of the pair of lead frames is provided, the length of the lead frames can be changed according to a desired shape of the secondary mold body.
The present invention provides a method for fabricating the photocoupler described above, comprising the steps of: fixing the primary mold body by vertically sandwiching the primary mold body between the pair of lead frames; bending the pair of lead frames in a predetermined direction while pinching base portions of the lead frames; releasing the primary mold body from the vertically sandwiched fixed state to form a mold space; and injecting a light-shading resin into the mold space, to form the secondary mold body.
According to the invention, a-photocoupler is fabricated by fixing the primary mold body by vertically sandwiching between the pair of lead frames, bending the pair of lead frames in a predetermined direction while the base portions of the lead frames are pinched, and forming the secondary mold body by injection of a resin. Therefore, the secondary mold body can be formed with the minimum resin amount. As a result, it is possible to fabricate a photocoupler which can be mounted on an object without necessitating large mount area therefor.
In the invention, it is preferable that, prior to the injection of the light-shading resin into the mold space, a position of the primary mold body with the bent lead frames in the mold space is corrected.
According to the invention; the position of the primary mold body with the bent lead frames in the mold space is corrected prior to the injection of the light-shading resin into the mold space. Therefore, it is possible to form the secondary mold body with the primary mold body placed in a proper position in the mold space.
In the invention, it is preferable that, prior to the injection of the light-shading resin into the mold space, part of faces defining the mold space is made to protrude in the mold space.
According to the invention, part of the faces defining the mold space is made to protrude in the mold space prior to the injection of the light-shading resin into the mold space. Therefore, the volume of the mold space into which the light-shading resin is injected can be reduced. In addition, a concave portion can be formed on the resultant secondary mold body, and the top end of the bent lead frame maybe made to protrude from the concave portion.
In the invention, it is preferable that, prior to the bending of the lead frames, unnecessary portions of the lead frames are cut away.
According to the invention, since unnecessary portions of the lead frames are cut away prior to the bending of the lead frames, it is possible to cut away unnecessary portions of the lead frames that may otherwise protrude from the resultant secondary mold body before the formation of the secondary mold body. Therefore, a photocoupler can be easily fabricated with good precision without occurrence of protrusion of unnecessary portions of the lead frames from the resultant secondary mold body.
According to the present invention, it is possible to provide a photocoupler capable of reducing the mount area required to mount the photocoupler on an object by eliminating a structurally unnecessary portion, and a method and apparatus for fabricating such a photocoupler.
With the recent improvement in substrate wiring technology, objects on which photocouplers are mounted have attained high performance and downsizing, and devices have been mounted on the objects with higher mount rate. In these circumstances, according to the present invention, it is possible to reduce the mount area required to mount the photocoupler on an object.
To state in more detail, a photocoupler must be fabricated in consideration of the following points: double transfer molding for forming the primary mold body and the secondary mold body, the positional relationship of the lead frames supporting the light-receiving device and the light-emitting device inside the photocoupler, securing of a space for placing the top ends of the lead frames to be soldered to an object on which the photocoupler is mounted, and the like. By use to the photocoupler fabrication apparatus and method according to the present invention, it is possible to fabricate a photocoupler which can be mounted on an object without necessitating large mount area, in addition to satisfying the above fabrication requirements.